This line of thought implies among other things (_a_) the view that whereas there is no ground for admitting the existence of _incomplete substances_, there is ground for distinguishing between _complete and incomplete natures_; (_b_) the view that from the union or conjunction of an actual multiplicity of substances, each remaining unaltered and persisting in its existence actually distinct from the others, there _can_ arise one single complete nature—a nature which will be _one being_ simply and really, _unum ens per se et simpliciter_, and not merely an aggregate of beings or an accidental unity, _unum per accidens_,—and there _does_ arise such a nature whenever the component substances not merely co-operate to discharge certain functions which none of them could discharge separately (which indeed is true of an accidental union, as of two horses drawing a load which neither could draw by itself), but when they unite in a more permanent and intimate way according to what we call “natural laws” or “laws of nature,” so as to form a new fundamental principle of such functions.(284) These views undoubtedly owe their origin to the belief that certain facts brought to light by the physical and biological sciences in modern times afford strong evidence that the elementary material constituents of bodies, whether inorganic or living, remain _substantially unaltered_ while combining to form the multitudinous _natural kinds_ or _natures_ of those living or non-living material things. It was to reconcile this supposed _plurality_ of _actually distinct_ and _diverse_ substances in the individual with the indubitable _real unity_ of the latter, that these philosophers distinguished between substance and nature. But it is not clear that the facts alleged afford any such evidence. Of course if the philosopher approaches the consideration of it with what we may call the atomic preconception of material substances as permanent, unchangeable entities, this view will preclude all recognition of _substantial_ change in the universe; it will therefore force him to conclude that each individual, composite agent has a unity which must be _less_ than substantial, and which, because he feels it to be _more_ than a mere accidental or artificial unity, he will describe as _natural_, as a union to form _one nature_. But if he approach the evidence in question with the view that substantial change is possible, this view, involving the recognition of incomplete substances as real, will remove all necessity for distinguishing between substance and nature, and will enable him to conclude that however various and manifold be the activities of the individual, their co-ordination and unification, as proceeding from the individual, point to a